Many synthetic, cloth-like materials are used in protective garments of one type or another. These materials can be thermoplastic or thermoset and are formed in both woven and non-woven configurations. These synthetic cloth-like materials include "Tyvek" which is a trademark of E.I. Du Pont de Nemours and Co., Wilmington, Del. 19898; "Duraguard" and "Safeguard" which are trademarks of Kimberly Clark Corp., Roswell, Ga. 30076; "Celestra" which is a trademark of Crown Zellerback Corp., Washougal, Wash. 98671; and "Duralace" which is a trademark of Chicopee Manufacturing Co., Chicopee, Ga. 30501. These materials are utilized as substitutes for cloth and pulp-paper in disposable clothes for medical, industrial and retail markets, as well as for other purposes.
In addition to the foregoing, laminated materials comprising a film and a substrate are also known in protective garments As described in Goldstein U.S. Pat. No. 4,272,851, materials such as "Tyvek" are conventionally laminated to a film of polyethylene, for example, and made into protective garments. U.S. application Ser. No. 06/920,361, the entire disclosure of which is incorporated herein by reference, discloses a high barrier, multilayer polymer film structure laminated onto a substrate.
The migration by chemicals through a complex laminated material involves a sequence of process steps including sorption, diffusion, and desorption, the combination of which is defined as permeation. There are a number of factors which influence the rates that each of these process steps will occur, or whether each step will occur at all. The various factors which govern the permeation rates include degradation of the laminate by the chemical, temperature, pressure, thickness, solubility, stereochemistry, concentration, state, vapor pressure and viscosity, among other variables.
If the chemical from which protection is sought is a liquid, the rate-limiting step becomes diffusion, and the sorption and desorption effects can be neglected. This diffusion, under ideal circumstances, is governed by the solubility and stereochemistry of the chemical and the protective material relative to each other.